Numerical modeling of injection/compression molding for center-gated disk. II. Effect of compression stage

摘要

In the accompanying paper, Part I, we have presented a physical modeling and the associated numerical analsysi of the injection molding process with a compressible viscoelastic fluid model. In Part II, effects of the compression stage in the injection /compression molding process are presented. Numerical results showed that the injection/compression molding process reduced birefringence as compared with the injection molding process. In this respect, the injection/compression molding process seems to be more suitable for manufacturing precise optical products of good optical quality than the injection molding process. Effects of the packing stage on the birefringence distribution in the injection/compression molding process were found to be similar to those in the injection molding process. Our numerical results show that the birefringence becomes smaller as the melt temperature gets higher and the closing velocity of the mold gets smaller with the flow rate and the mold temperature affecting the birefringence insignficantly. As far as the density distribution is concerned, the flow rate, melt temperature, and mold closing velocity have insignificant effects on the density distribution in comparison with the mold temperature. (Example material: polystyrene.)